Brain Lesions

Reviewed on 11/1/2022

What Facts Should You Know About Brain Lesions?

Headaches, personality changes, nausea, and vomiting are signs and symptoms of brain lesions.
Headaches, personality changes, nausea, and vomiting are signs and symptoms of brain lesions.
  • Brain lesions (lesions on the brain) refers to any type of abnormal tissue in or on brain tissue.
  • Major types of brain lesions are traumatic, infectious, malignant, benign, vascular, genetic, immune, plaques, brain cell death or malfunction, and ionizing radiation. Other chemicals and toxins have been associated with brain lesions as well.
  • Brain lesions have many different causes that are related to the types listed above.
  • Risk factors for the development of brain lesions include any behaviors that increase the chances a person will suffer trauma to their head, exposure to certain infections, smoking and exposure to tobacco smoke, exposure to many types of chemicals and ionizing radiation, a poor diet, and alcohol use. Genetic risk factors are unavoidable.
  • Signs and symptoms of most brain lesions are related to the type of lesion. However, some symptoms often found in patients with different types of brain lesions include headaches (recurrent or constant), nausea, vomiting, decreased appetite, changes in mood, changes in personality, behavioral changes, cognitive decline, inability to concentrate, vision problems, hearing and balance problems, muscle stiffness, weakness, numbness or paralysis, change or loss of sense of smell, memory loss, confusion, seizures, and coma.
  • Seek prompt medical care if any of the above symptoms develop.
  • Diagnosis of brain lesions begins with the patient's medical and family history, their signs and symptoms, and the physical exam. Usually, several blood tests are ordered and many patients will undergo a CT scan or MRI of the brain. Definitive diagnosis for some brain lesions is based on the examination of biopsy tissue taken from the brain lesion.
  • Treatment of brain lesions depends on the brain lesion type, the patient's age, their overall health problems, and the decision to proceed with a treatment plan agreed on by both the patient and their medical treatment team. Depending on the brain lesion type, treatment may include antibiotics, brain surgery, radiation therapy, chemotherapy, or a combination of these treatments. Other lesions have no effective treatment except for the use of medications that may reduce symptoms and impede the progression of the disease.
  • Complications of brain lesions may arise from the disease process itself or from the treatment modalities, and can range from minor complications (nausea and vomiting) to severe (symptoms become worse, seizures, coma, or even death).
  • Prognosis for brain lesions is highly variable depending on the type of lesion, the age and health condition of the patient, and how effective treatments are for the patient. The range of prognosis varies from good to poor, with the prognosis in some lesions declining as the patient's disease progressively worsens over time (usually years).

What Are Brain Lesions?

"Lesions on the brain" is a phrase that many people use to find information about brain problems. The phrase is non-specific and indicates that the searcher may desire an introduction to this vast, highly detailed, and complicated subject. The design of this article will be to introduce the readers to a series of topics about brain lesions and to provide them with some key terms and ways to delve deeper into the topic if they so desire.

First, however, the reader needs to understand what is meant by "lesions on the brain". The term "lesion" is derived from the Latin word "laesio" meaning injury. Medically speaking, the term lesion refers to any abnormal tissue found on or in a person or organism usually caused by disease(s) or injury. Consequently, the "lesions on the brain" phrase covers all topics related to abnormal tissue that can be found on or in the brain.

A presentation of topics introducing the reader to types, causes, risk factors, symptoms, diagnosis, treatment, complications, prevention, and prognosis for brain lesions will be presented. Finally, this article cannot cover every brain lesion (there are over 120 different named brain tumors alone), so the reader is advised once they have read this article, to then go to the links and references in this article to obtain more detailed information about specific diseases.

What Are the Types of Brain Lesions?

Brain lesion types are vast, but there are terms and categories that help to classify the various conditions. The major types of brain lesions are listed below, along with an example within that category:

  • Traumatic: gunshot wound to the brain
  • Infectious: meningitis
  • Malignant (cancerous): glioma
  • Benign (non-cancerous): meningioma
  • Vascular: stroke
  • Genetic: neurofibromatosis
  • Immune: multiple sclerosis
  • Plaques (deposits of substances in brain tissue): Alzheimer's disease
  • Brain cell death or malfunction: Parkinson's disease
  • Ionizing radiation: radiation exposure leading to the death of normal brain tissue

There are other types of brain lesions that have been associated with exposure to chemicals (nitrites), toxins (pesticides), and electromagnetic fields, but because research is ongoing with these associations, some investigators may consider these as potential causes of brain lesions.

Finally, there are brain lesions that are of mixed types (for example, genetic with brain cell death as seen in Huntington's disease). Although these general types listed above are not accepted by all medical professionals, they are a starting point for many to help caregivers explain what type of brain lesion an individual may have.

What Causes Brain Lesions?

From the above description of brain lesion types, it is evident that the different types are arranged, in general, according to different mechanisms that lead to brain cell changes which produce various brain lesions. The causes, however, can be further categorized. The following is a list of causes containing more specific subsets and descriptions:

  • Trauma: penetrating or blunt. Blunt trauma may be further subdivided to include with or without skull fracture. Trauma results in damaged or destroyed brain tissue with immediate and/or delayed (hours to days, usually) symptoms.
  • Infectious: Brain lesions caused by a wide variety of pathogenic agents ranging from viruses, bacteria, fungi, and parasites. Some may develop symptoms quickly over hours to days (such as in viral and bacterial meningitis) or over many years (such as in the parasitic infection Cysticercosis).
  • Malignant: Malignant brain lesions subtypes are termed "primary" if they arise from the brain tissue cells (such as gliomas and medulloblastomas) and "secondary" if they originate in other body organs and spread (metastasis) to the brain (such as lung, breast, and colon cancers). Secondary brain lesions are more common than primary brain lesions. Some lesions develop fairly fast (weeks to months), while others may develop more slowly. In addition, malignant lesions are often graded, which means they are assigned a number (I, II, II, or IV) based on their appearance under a microscope. Grade I tumors are less aggressive and tend to grow and spread more slowly, while grade IV tumors are highly aggressive and tend to grow and spread more rapidly.
  • Benign (non-cancerous): Brain lesions composed of abnormally growing cells that are non-cancerous (though a rare few may contain some cancer cells, mainly grade I). They may cause symptoms if they become large and compress other normal brain tissue or interfere with the blood supply to the brain. They usually develop slowly (for example, meningiomas).
  • Vascular: Three subtypes of vascular brain lesions exist; 1) arteriovenous malformations (weak vascular areas that may leak or burst, causing blood to leak into brain tissue), 2) abnormal growth of vessels in the brain (hemangioblastomas associated with von Hippel-Lindau disease), and 3) the most frequently encountered vascular problem, strokes (also termed cerebral vascular accidents or CVA's). Most strokes are caused by clots (about 85%) which cause brain cell damage or death by reducing or cutting off the blood supply to areas of the brain. Except for the long-term development of diseases like von Hippel-Lindau, vascular brain lesions generally produce symptoms within minutes to hours.
  • Genetic: Errors in human DNA or certain DNA sequences in the genetic makeup of some individuals can lead to brain lesions, such as neurofibromatosis or familial British dementia. Most of these lesions develop over years.
  • Immune: The individual's immune system mistakenly attacks and attempts to destroy brain tissue components, such as myelin (a sheath surrounding nerve cells). The resulting scar tissue can be seen in multiple sclerosis, for example. These types of lesions usually progress in development over years.
  • Brain cell death or malfunction: The cause of certain brain lesions, like those seen with Parkinson's disease, is due in part to the malfunction and death of brain cells that produce dopamine. However, the underlying cause may be related to genetics, toxic exposures, or various other combinations of potential causes. Development usually progresses over years.
  • Plaques (deposits of substances in brain tissue): Deposits of materials such as Lewy bodies, amyloid plaques, and neurofibrillary tangles or bundles in brain tissue are associated with several diseases, most notably Alzheimer's disease. However, it is not clear whether the deposits are the primary cause or if they are the secondary results of an underlying (and as of yet) unidentified cause. Development usually progresses over years.
  • Ionizing radiation: X-rays, gamma rays, and other types of radiation, when intense enough or if acquired sequentially in high levels, can disable and destroy brain cells, as well as other cell types.

Many brain lesions may have more than a single cause and are often associated with multiple risk factors, which some researchers believe may be the cause, although a direct link to the risk factor(s) is often difficult or unlikely to be proven by researchers.

What Are Brain Lesion Risk Factors?

The following are considered risk factors for the development of brain lesions by most experts:

  • Any type of activity that can lead to head trauma
  • Infections that may produce brain lesions include HIV, Toxoplasma, Streptococcus, Neisseria, Haemophilus, pork tapeworm, rabies, roundworms, viruses, and many others
  • Family history of brain cancer or brain tumors
  • Known inherited genetic disorders
  • Radiation exposure to the head
  • Cigarette smoking and other tobacco smoke exposure
  • Environmental toxins such as chemicals that are used in oil refineries, embalming, and the rubber industry

What Are the Signs and Symptoms of Brain Lesions?

Most of the signs and symptoms encountered with brain lesions, except for obvious head trauma, are not specific and can be seen in many other diseases. Even with head trauma, there are symptoms that may be subtle. Signs and symptoms will be divided into three sections.

  1. The first section will present some signs and symptoms that often help medical caregivers begin to narrow the diagnostic possibilities.
  2. The second section will discuss the many non-specific, but important signs and symptoms that may occur at some time in many individuals with diverse causes of brain lesions.
  3. The third section will present some signs of brain lesions that are more specific to infants and children, although children can exhibit most of the signs and symptoms listed in sections one and two.

Signs and symptoms of some prominent types of brain lesions are as follows:

  • Trauma: Penetrating or skull-depressed head wounds, facial bruising, scalp hematomas, scalp lacerations, history of falls, fights, and auto accidents (especially if the patient had any loss of consciousness or is in a coma)
  • Infectious: Fever, stiff neck, and headache (about 1-3 days) that may progress to confusion and seizures may be seen with meningitis.
  • Vascular: Sudden or rapid onset of a headache (minutes to days) often described as the worst headache ever, and sometimes associated with fainting, may be seen with a leaking or ruptured brain aneurysm. Sudden or rapid onset (minutes to hours) of slurred speech, weakness, numbness of an extremity, or a facial droop may be seen with strokes.
  • Malignant: Onset over days to months of headaches, weakness, personality or mental status changes, or seizures in patients with a known history of cancer (in organs other than the brain) is concerning for metastatic brain lesions (for example, lung cancer that has spread to the brain).

Though the signs and symptoms listed below in this second section may also develop with the previously listed conditions, the acuity of those conditions is what often persuades these individuals to seek emergent medical evaluation. The signs and symptoms below are nonetheless important, but less specific and may occur with almost all types of brain lesions. They may develop over days to years and are more typical of benign, genetic, and immune brain lesions; and are often characterized by brain cell death, plaque formation, and other causes related to brain lesion formation:

  • Headaches (recurrent or constant)
  • Nausea, vomiting, decreased appetite
  • Changes in mood, personality, behavior, and cognitive abilities
  • Vision, hearing, and balance problems
  • Muscle stiffness, weakness, or paralysis
  • Change or loss of sense of smell
  • Memory loss, confusion

Symptoms that may occur late in the progressive decline of individuals are seizures and coma, which often precede the person's death.

What Are Brain Lesion Signs and Symptoms in Infants and Children?

The third set of signs and symptoms are those that are relatively unique to infants and children, however, they are not necessarily specific to a particular type of brain lesion. Nonetheless, they are signs and symptoms that indicate that a problem with the brain is likely and that the child needs immediate medical evaluation:

  • Bulging fontanelle (where the skull has not yet closed—a soft, small area of thin membrane and skin covering the brain that can expand or bulge outward when the brain experiences abnormal pressure from any source)
  • Abnormal red reflex in the eye (may be due to cataracts or retinoblastoma)
  • Skull sutures not closing normally (due to brain tissue expansion or pressure)
  • Babinski reflex (up-going big toe and other toes fan out when the sole of the foot is firmly stroked) if present in children over 2 years old, is an indicator of a problem in the central nervous system (CNS)

Occasionally, adults with brain injury will also develop a Babinski reflex indicating nerve pathway damage between the spinal cord and the brain.

When to Seek Medical Care for Brain Lesions

Medical care should be sought immediately for the following conditions:

  • Penetrating or skull-depressed head wounds
  • Fever, stiff neck, and confusion
  • Sudden or rapid onset of an intense headache
  • Sudden or rapid onset of slurred speech, a facial droop, or weakness and numbness of an extremity
  • Relatively rapid onset of personality or mental status changes in patients with a known history of cancer
  • New onset of seizure or loss of consciousness
  • Changes in mental status, such as excessive sleepiness, memory problems, confusion, or inability to concentrate
  • Visual changes
  • Bulging fontanelle in infants

The other signs and symptoms listed in the previous sections of this article should also persuade patients or their caregivers to seek prompt medical attention.

How Do Doctors Diagnose Brain Lesions?

An accurate medical history, family history, and physical exam may often allow a presumptive diagnosis to be made by the doctor. However, in most situations, the physician will conduct other tests to gather further data and information in order to establish a definitive diagnosis.

Although various blood tests may be ordered, imaging studies of the brain using a CT scan or MRI will likely be the most important tests to evaluate and visualize brain lesions. The type of imaging study initially ordered will generally depend on the signs and symptoms of the patient.

A lumbar puncture (spinal tap) may also be performed to evaluate for meningitis or other neurologic conditions, depending on the clinical scenario. In addition, some patients may undergo neurological and physiological testing. All of these tests are important because they may yield evidence that a condition other than a brain lesion is causing the patient's problem. Alternatively, the tests may provide definitive evidence that the presumptive diagnosis suspected of causing a brain lesion is correct.

However, sometimes the definitive diagnosis is made by a tissue biopsy of the brain lesion. A surgeon, using small instruments, can remove a sample of brain tissue, which can then be examined microscopically, leading to a final diagnosis (and grading of the brain lesion if it is cancer). In some situations, such as brain lesions due to trauma, a biopsy is not necessary for a diagnosis. In other situations, the diagnosis is not confirmed until autopsy (for example, in many people with Alzheimer's disease).

What Are Treatments for Brain Lesions?

Treatment options for brain lesions are often complicated and usually, are decided by a team of physicians with the consent of the patient or the patient's representative. The treatment for some conditions, such as bacterial meningitis, is generally straightforward and requires the use of antibiotics and steroids. However, other brain lesions may require extensive medical and surgical treatment. For example, many patients may need to undergo brain surgery to:

  • Relieve pressure on the brain
  • Repair an aneurysm
  • Remove a tumor
  • Evacuate blood that is compressing against brain tissue

The treatment for stroke depends on the early recognition of stroke symptoms and may, in some cases, be treated with anti-clotting agents such as tissue plasminogen activator (tPA) to restore blood flow to oxygen-deprived brain tissue. However, with these treatments, there are risks and potential complications (as described in the Complications section).

Brain cancer lesions oftentimes require the most complex treatment. Treatment plans are generally designed by a team of physicians taking into account the individual needs and wishes of the patient. This treatment plan is based on the patient's age and overall condition, the type of cancer, the grade of cancer, whether it is metastatic, and the expected response and success rate seen with the particular cancer type.

Surgery, radiation, and chemotherapy are the mainstays of treatment for brain cancer. Some patients may require one type of therapy, whereas other patients may need two or all three types of treatment for their brain cancer. Patients and their physicians need to discuss all the proposed treatments and their inherent risks and side effects before deciding on which treatments are appropriate and desired.

Other brain lesions are more difficult to treat because the treatments, at best, do not cure the disease but only reduce the symptoms or slow the advancement of the disease. Most of the genetic, immune, brain cell death, plaque forming, and ionizing radiation brain lesions are in this category. The classic example is Alzheimer's disease (plaque forming and brain cell death), which can be treated with several different medications that may delay its progression and slow the behavioral changes seen with the disease. As with brain cancer, treatment regimens are individually designed for each patient with these diseases. Most of these diseases are treated with medications only, though there are a few exceptions such as the mixed types of diseases (genetic and vascular, as are found in some aneurysm formations).

Every patient usually has an individualized treatment protocol. Even though patients may share the same diagnosis, their treatment protocols may be quite different depending on various factors such as age, overall medical health, and the severity of the brain lesions. If patients or their families have questions or concerns about certain aspects of their treatment, they should seek answers from their treatment team members, or seek a second opinion from other qualified physicians.

What Are Complications of Brain Lesions?

Although the complications of any brain lesion are numerous and often dire, they are generally related to either the progression of the brain lesion itself or to complications from treatment. Left untreated, many brain lesion types may eventually lead to the development of complications such as for example respiratory depression, loss of muscle function, or widespread brain cell death leading to seizures and coma.

Other serious complications include severe disability (for example, loss of memory or speech, loss of limb function, confusion, or combative personality changes). Dangerous behavior patterns (for example, medication errors, getting lost while driving or taking a walk, leaving stove burners on, as well as others) may occur in some patients, especially those that develop slowly progressive diseases like Alzheimer's disease.

Complications from attempts to treat various brain lesions can also be severe. A brain surgeon often has to go through normal brain tissue to reach the brain lesion, both for diagnosis and treatment. Complications may include injuring otherwise normal brain tissue, thus making the patient's symptoms worse. There is a similar risk involved with radiation therapy, as the destructive beam may damage or affect surrounding normal tissue. Chemotherapy, while designed to target specific cancer cells, may also affect some of the body's other normal cells resulting in cell damage or cell death. Nausea, vomiting, dehydration, weakness, and susceptibility to infection may also result.

Similar complications may occur when diseases characterized by a slow, progressive brain lesion are treated with multiple drugs. Patients with strokes treated with the medication tPA may develop severe, life-threatening bleeding, which may actually worsen the symptoms from the original stroke, or even cause death. Because there are inherent severe risks in treating certain brain lesions, it is imperative that patients or their surrogates are well informed about the patient's prognosis, as well as the risks and benefits of the various treatment options. Oftentimes, difficult decisions must be made between the treatment team and the patient or their representatives.

Is It Possible to Prevent Brain Lesions?

In some instances, certain brain lesions can be prevented, though not all types can be completely prevented. For some brain lesion types, reducing various risk factors can lessen the chances the brain lesions will develop; however, if they do, there are sometimes ways to slow the progression of symptoms. Each type of brain lesion varies somewhat in its prevention. The following list, though not entirely comprehensive, provides readers with the various types of brain lesions, and recognized preventive measures.

  • Traumatic: Avoid risky behaviors, wear protective equipment (bicycle or motorcycle helmets), and use seatbelts in automobiles
  • Infectious: Avoid any contact with infected individuals, especially those diagnosed with meningitis. Some people may need to take antibiotics to prevent the disease if exposed.
  • Malignant (cancerous): Stop tobacco smoking and avoid places where you are exposed to smoke, avoid environmental or work-related chemicals associated with cancer, wear protective clothing and masks when appropriate, and undergo routine checkups and tests (for example, prostate, testicle, and breast exams, Pap smear, mammograms, colonoscopy, etc.) to detect any cancers early when they are more easily treated.
  • Benign (non-cancerous): Although no good prevention methods are known (other than those possible for cancer), early diagnosis and treatment may prevent more serious complications if the benign tumor is removed while relatively small in size.
  • Vascular: Arteriovenous malformations, if found before a significant bleed into the brain occurs, can be clipped (surgically neutralized) before they cause serious brain damage. Strokes may be reduced or prevented by maintaining a healthy lifestyle (for example, a healthy diet, exercising, avoiding smoking, limiting alcohol intake, maintaining a healthy weight), and keeping your blood pressure and cholesterol low. If a person has diabetes, proper glucose level control can help prevent many cardiovascular diseases. Individuals with high blood pressure and other medical problems should take their medications as prescribed by their physician. People with a history of strokes or transient ischemic attacks (TIA's or mini-strokes) are advised in most situations to take 81 mg of aspirin (a baby aspirin) once a day to help prevent subsequent strokes and cardiac problems.
  • Genetic: Other than not being part of a certain gene pool (which people have no control over), the only way to help prevent or slow these conditions is to avoid any situations or chemicals that may trigger the genomic expression or accelerate the genetic process. Unfortunately, most of these compounds are only suspected or associated with brain lesion development.
  • Immune: Generally speaking, there is no current effective way to completely prevent immune-mediated brain lesions, however, medications may help to prevent or halt relapses, as well as slow the overall progression of the disease.
  • Plaques (deposits of substances in brain tissue): Alzheimer's disease is the major disease in this type of brain lesion category. Age and genetics likely play a role in its development, but these factors are not controlled by an individual. However, most investigators suggest that a healthy diet, routine exercise, and intellectual and social stimulation are all likely to slow the advancement of this disease. Additionally, there are medications that may help delay or prevent symptoms from becoming worse, though the disease will not be halted altogether.
  • Brain cell death or malfunction: Since the causes of these brain lesions are unknown, there is no effective treatment to stop the advancement of these lesions. A classic example of such a disease is Parkinson's disease. Like Alzheimer's disease, age, and possibly genetics, may play a role in its development and most investigators suggest that a healthy diet, routine exercise, and intellectual and social stimulation are all likely to slow the advancement of this disease. Fortunately, some knowledge about the neuropathology of Parkinson's disease (the loss of dopamine-producing brain cells) has led to the development of medications that in some patients, markedly reduce symptoms for some time. However, as in Alzheimer's disease, the disease is progressive.
  • Ionizing radiation: Radiation exposure may be prevented by taking appropriate precautions, especially barrier shielding for those working around sources of ionizing radiation (X-ray technicians, radiologists, researchers, workers in the nuclear power industry, and others) in order to prevent ions from disrupting or killing brain cells (and other cell types). In addition, though ionizing radiation is used by physicians to shrink and kill tumors and cancer cells, in some instances, normal brain tissue and other types of cells may be damaged or killed. Precise and careful targeting to avoid major damage to normal tissue can help mitigate this problem.

What Is the Prognosis for a Brain Lesion?

Because of the many different types of brain lesions, the prognosis and outcomes of brain lesions are variable. However, with most brain lesion types, the more brain tissue that is damaged or killed by a brain lesion, the worse the prognosis is for the person. Fortunately, the reverse (little damage, good prognosis) is also generally true, but is mainly limited to lesions caused by mild trauma, strokes that affect a very small brain tissue area, a few rapidly treated infections, and occasionally, a few benign and malignant tumors that are effectively treated.

For some brain lesion types, the damage to some brain tissue is not reversible, so the prognosis may be only fair to good, as long as the person's problems do not progress. Another problem with prognosis is that some brain lesions may recur (for example, strokes and brain cancers), while others (genetic, immune, and plaque-forming and brain cell death types exemplified by Huntington's disease, multiple sclerosis, Alzheimer's disease, and Parkinson' disease) are simply progressive with no effective definitive cure available. The prognosis in the short term may be good if the symptoms respond to treatment, but the long-term prognosis usually is considered to be, at best, fair to eventually poor (perhaps many years after the initial diagnosis), due to their progressive nature.

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Brain Lesions Symptoms

Severe Brain Lesion - Coma symptoms

The main symptom of a coma is unconsciousness. A patient in a coma will have no conscious response to external stimuli and may appear to be in a deep sleep.

The patient in a coma may exhibit spontaneous body movements. Patients may shake or jerk abnormally, and the eyes may move. If the coma is severe, even basic body functions such as breathing may be affected.

Reviewed on 11/1/2022
Medically reviewed by Joseph Carcione, DO; American board of Psychiatry and Neurology

United States. CDC. "Preventing Stroke: What You Can Do." Apr. 30, 2015.

"Brain tumor - children." Reviewed Sept 4, 2015.

"NNDS Brain and Spinal Tumors Information Page." National Institute of Neurological Disorders and Stroke. Updated Jan 22, 2016.

"Can Alzheimer's Disease be Prevented? So, What Can You Do?" National Institute on Aging. Updated Jul 29, 2016.